1. Field of the Invention
The present invention relates to an automatic white balance adjustment system, and more particularly, to an automatic white balance adjustment system, wherein a red cathode voltage detected by a cathode voltage detection circuit, a green cathode voltage detected by the cathode voltage detection circuit, and a blue cathode voltage detected by the same are read by an analog-to-digital (A/D) signal conversion port of a microcomputer, and the readings are processed by means of software provided within the microcomputer.
2. Description of the Related Art
Various types of automatic white balance adjustment systems for use with a television set have already been proposed.
For example, in an automatic white balance adjustment system described in Japanese Patent Unexamined Publication No. Hei. 7-170529, cathode currents corresponding to detection pulses cyclically inserted in a predetermined horizontal period within a vertical blanking period are measured. The thus-measured currents are compared with a reference value, thereby outputting comparison results. By means of the thus-output comparison results, the cathode currents corresponding to detection pulses are controlled so as to become substantially equal to the reference value.
In another automatic white balance adjustment system described in Japanese Patent Unexamined Publication No. Hei. 9-271037, at the time of adjustment a reference white level voltage and a reference black level voltage are imparted to a d.c. voltage level/gain adjustment circuit at predetermined timings. Detected cathode currents are compared with a reference current, and data pertaining to comparison results are produced and stored in a non-volatile memory. Further, the data are read from the memory and are supplied to the d.c. voltage level/gain adjustment circuit as data for adjustment.
As described above, various types of systems for adjusting the white balance of the television set have already been proposed. However, each of the systems uses a single value as a reference value for determining and adjusting all the primary color signals; i.e., RGB signals. For this reason, desired color temperatures cannot necessarily be achieved.
The present invention has been made to solve the above problem, and an object of the present invention is to provide an automatic white balance adjustment system arranged so as to control the mixing ratio of the respective RGB primary color signals to a certain ratio, by separately setting the reference values for the respective primary colors R, G, and B.
To achieve the above object, according to the present invention, there is provided an automatic white balance adjustment system comprising: a color signal reproduction circuit which demodulates respective RGB primary color signals from a composite video signal and has a white balance adjustment section; a picture tube drive circuit which drives and displays images on a picture tube so as to correspond to the RGB primary color signals reproduced by the color signal reproduction circuit; a cathode voltage detection circuit which detects a cathode voltage applied to a red cathode electrode, a cathode voltage applied to a green cathode electrode, and a cathode voltage applied to a blue cathode electrode of the picture tube; a storage circuit which stores in advance comparison reference values set for the RGB primary color signals in order to control the RGB primary color signals so as to achieve a white balance in a given ratio; and a control circuit which, when detection pulses of predetermined IRE values corresponding to the respective RGB primary color signals are output from the picture tube drive circuit, reads the red cathode voltage, the green cathode voltage, and the blue cathode voltage, all being detected by the cathode voltage detection circuit, and compares the thus-read detection voltages with the corresponding comparison reference values stored in the storage circuit, to thereby control the white balance adjustment section of the color signal reproduction circuit such that the detected voltages coincide with the corresponding comparison reference values.